The present invention relates to telecommunication in general and to simultaneous voice and data communication using the Internet protocols (IP). In particular the invention relates to a modem which allows access to the PSTN network (or to the ISDN network) and to IP-based networks from the subscriber end of a subscriber line.
A conventional data modem provides a digital bearer for digital information. A conventional data modem is typically connected between a computer and a subscriber line. A communication application running on the computer provides access to the Internet over PSTN. The subscriber line will be busy to the PSTN network if the communication application is involved in an ongoing IP session, such as surfing on the Internet, sending or receiving e-mail, running an IP phone application.
While an application is involved in an IP session it is not possible to make an outgoing call from a normal telephone connected to the same subscriber line as the modem because the subscriber line is busy.
In Swedish Patent Application No. 960 2212-4 there is described a telephony server allowing a user, which is involved in an IP session, to receive telephony calls from the PSTN/ISDN network to a personal computer used for the IP session. An incoming call directed to any member of the user""s family can only be handled on the personal computer. It cannot be handled on another telephone device. Likewise another member of the family than the one engaged in the IP session cannot make an outgoing call over the normal telephone.
A DSVD modem is a modem that allows for digital simultaneous transmission of voice and data on a single line. To achieve this properly a DSVD modem must communicate with another DSVD modem. A DSVD modem comprises means for multiplexing packetized speech information and for sending the multiplexed information over a single link. A DSVD modem supports two independent sessions such as a telephony session simultaneously with an Internet session but has no means for accessing PSTN/ISDN services in order to establish such parallel sessions. A DSVD modem does not support the control procedure of analogue phones such as for example control procedures for off hook, on hook, DTMF signalling (dual tone multifrequency signalling), generation of ring signals, generation of ring tones, hook flash signalling.
One object of the present invention is to provide a modem which allows an outgoing call as well as in incoming call on a normal telephone while simultaneously a communication application running on a personal computer is involved in an ongoing IP session over the modem.
Still another object of the invention is to provide a modem for autonomous, simultaneous access to the services of a switched telephony network, such as PSTN or ISDN, and to the services of an IP (Internet Protocol)based network, such as the Internet or an intranet, using the IP protocol.
Still another object of the present invention is to provide a modem that has at least two analogue telephony interfaces so as to allow a subscriber to have two different telephones which can be operated independently and simultaneously.
Still another object in accordance with the invention is to provide a modem allowing for internal telephony between a telephony application running on a PC and a normal telephone and allowing for internal telephony between two telephones connected to the IP modem in a subscriber""s home.
A further objective of the invention is to provide a modem that allows connection to a home LAN (local area network in a subscriber""s home) using the IP protocol.
Still another objective of the invention is to provide a modem that allows communication with devices, which are connected to the home LAN and which all support communication using the IP protocol, from an IP based network such as the Internet.
The above objects are attained with a modem of the general kind indicated in the attached claims.
The modem in accordance with the invention uses, in a manner known per se, the analogue transport capabilities of an analogue subscriber line to provide a two directional, 28.8 kb/s, or higher, digital transport capability.